Authority change mechanism

ABSTRACT

Authority change mechanism includes a relatively low ratio change mechanism interposed between an input shaft and output cam whose input range has been extended by the same factor as the ratio change mechanism. In the secondary high authority mode of operation, the same output command is achieved as in the primary mode at less input command. At higher input commands the output command in the high authority mode is greater than the maximum output in the primary mode, and by limiting use of the extended portion of the cam to the high authority mode, its configuration may be such as to increase the total output in the high authority mode by a much higher factor during high inputs for high maneuverability.

1 Nov. 27, 1973 AUTHORITY CHANGE MECHANISM [75] Inventor: Richard PaulHeinti, Kalamazoo,

Mich.

[73] Assignee: Pneumo Dynamics Corporation,

Cleveland, Ohio [22] Filed: Mar. 27, 1972 [21] Appl. No.: 238,510

Primary Examiner-Charles J. Myhre Assistant ExaminerWesley S. Ratliff,Jr. Attorney-Stephen M. Mihaly [5 7] ABSTRACT Authority change mechanismincludes a relatively low ratio change mechanism interposed between aninput shaft and output cam whose input range has been extended by thesame factor as the ratio change mecha- 52 us. (:1. 74/96, ISO/79.2 Anism- In the Secondary high authority mode of Opera- 51 1m. 01. F16h21/44 tion, the Same Output Command is achieved as in the 58 Field ofSearch 74/96, 53, 54, 55, P y mode at less input command At higher input74/56, 834, 37 52 180/792 R 92 commands the output command in the highauthority A, 3 mode is greater than the maximum output in the primarymode, and by limiting use of the extended por- [56] References Citedtion of the cam to the high authority mode, its configuration may besuch as to increase the total output in UNITED STATES PATENTS 4 the highauthority mode by a much higher factor duriii? 21132 lliri 'fffflit"""iiiiifi'a/l li fi mg high inputs for high maneuverability- 3,055,2279/1962 Martin 74/97 10 Claims, 6 Drawing Figures 3,312,301 4/1967 Hagen180/792 R 3,496,874 2/1970 Findlay 74/834 OUTPUT INPUT #1 CAM SERVOOUTPUT C O M M A N D l 2 1 PRIOR ART 3 l PATENTEH IIIIII 21 ms INPUTINPUT 3.774.463 SHEET 10F 2 CAM OUTPUT SERVO TP T COMMAND U I 2 (PRIORART) 3 x 3 M P CAM CA RATIO OUT UT SERVO OUTPUT OUTPUT CHANGER CMD. 2 \5a (PRIOR ART) HIGH AUTHORITY MODE (RATIO CHANGE an) PRIMARY MODE soINPUT INPUT- /o 5 45. .5

UTPUT RATIO INPUT CAM O SERVO OUTPUT Pmimwnnvzv ms 3774.463

SHEET 20F 2 20 y l2 L4 I 6 22 2| '3 ll l8 HIGH AUTHORITY MODE RATIOCHANGE 4Z3 AT CAM INPUT OUTPUT PRIMARY MODE O 20 4O 6O 80 I00 I20 INPUT%AUTHORITY CHANGE MECHANISM BACKGROUND OF THE INVENTION This inventionrelates generally as indicated to an authority change mechanism forvarying the ratio of input to output in a predetermined controlledmanner to prevent degradation or loss of control in both the primary andsecondary modes of operation under normal input commands. I

For proper control of the movements of nose wheel steering systems forhigh speed aircraft and the like, authority change mechanisms areoftentimes used to provide more than one mode of operation for varyingthe functional relationship between the input and output displacement atdifferent speeds. At relatively high speeds, the functional relationshipbetween input and output is critical and should be kept relatively lowto insure proper control, whereas at relatively low speeds, there islittle or no danger of loss of control and accordingly the relationshipbetween input and output may be increased by a relatively large factorfor increased maneuverability in close quarters.

The main objection to previous authority change mechanisms was thatduring the secondary mode of operation they amplified the output by thesame high factor for all levels of input commands. This meant that ifthe operator through error or signal failure inadvertently selected thesecondary mode of operation at a critical time when good controlsensitivity was required, there was a degradation and possible loss ofcontrol even during relatively small inputs.

The usual high ratio changers also added to the cost and size of themechanism and suffered in accuracy and other characteristics.Objectionable interrupted or spring loaded cams or similarnon-continuous or nonpositive devices were also used in previousauthority change mechanisms.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principalobject of this invention to provide a relatively simple and reliableauthority change mechanism including a primary low authority mode ofoperation for critical control and a secondary high authority mode ofoperation for maneuverability which nevertheless also provides adequatecontrol during normal inputs, thereby preventing loss of control even ifthe high authority mode is inadvertently selected during a criticalperiod of operation.

Another object is to provide such an authority change mechanism which ismore accurate and more compact than previous known mechanisms utilizinglarge ratio changers.

Still another object is to provide such an authority change mechanismwhich only slightly amplifies the input signal during the secondary modeof operation under normal input commands and substantially amplifies theinput signal under high input commands.

Yet another object is to provide such an authority change mechanismwhose secondary mode output does not exceed the maximum primary modeoutput authority until a relatively high input is commanded.

These and other objects of the present invention may be achieved byproviding the authority change mechanism with a relatively low ratiochanger which only amplifies the input signal by a relatively smallamount. The ratio changer is placed between the input shaft and outputcam, and the input range of the cam is desirably e'xtended by the samefactor as the ratio changer. During the secondary mode of operation, themaximum output command obtainable in the primary mode is achieved atless input. Beyond that point the output command is greater in thesecondary mode, and by restricting the use of the extended portion ofthe cam only during the secondary mode of operation, its configurationmay be such as to increase the total output during the secondary mode bya much higher factor at high inputs for high maneuverability.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principles of the invention may beemployed.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings: FIG. 1 is aschematic diagram of a conventional drive mechanism for obtaining adesired functional relationship between the input and outputdisplacement in a low authority or primary mode of operation;

FIG. 2 is a schematic diagram of a conventional authority changemechanism including a high ratio changer for amplifying the output fromthe cam of FIG. 1 by a high factor during the high authority orsecondary mode of operation;

FIG. 3 is a graph showing the relative inputs and outputs obtainedduring the primary and secondary (high authority) modes of operation ofthe mechanism of FIG. 2;

FIG. 4 is a schematic diagram of a preferred form of authority changemechanism constructed in accordance with this invention;

FIG. 5 is a schematic isometric view showing the various components ofthe authority change mechanism of FIG. 4; and

FIG. 6 is a graph showing the relative inputs and outputs obtainedduring the primary and secondary (high authority) modes of operation ofthe mechanism of FIGS. 4 and 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to thedrawing and initially to FIG. 1 thereof, there is schematically shown aconventional drive mechanism 1 including a cam or function generator 2for modifying the functional relationship between the input and outputdisplacement to obtain the desired output command for a primary mode ofoperation. A servo 3 may be operated by the cam 2 to cause the actualoutput to follow the command, overcoming any output forces which may bepresent.

Such a primary mode of operation may be used to control such movementsas the nose gear steering system for an aircraft at high speeds when thefunctional relationship between the input and output displacement iscritical for proper control of the aircraft.

A second high authority mode of operation is also usually provided toincrease the relationship between the input and output displacement by acertain factor at low speeds for maneuvering the aircraft in closequarters.

A previous known authority change mechanism 4 shown in FIG. 2 achievedthe desired authority change using a relatively high ratio changer toamplify the output of the cam 2 of FIG. 1 by the desired factor.However, such relatively high ratio changers 5 had the disadvantage thatthey added to the cost and size of the device, and such high ratiochangers also suffered in accuracy and other characteristics. Moreover,in the high authority mode, any input resulted in an output which wasseveral times greater than the corresponding output in the primary modeas determined by the factor of the ratio changer.

The operation of the authority change mechanism 4 of FIG. 2 isschematically illustrated in FIG. 3 using a ratio change mechanismhaving an authority change ratio of three to one which results in anoutput for the high authority mode of three times the output for theprimary mode for the same input. This has the disadvantage that ifthrough operator error or signal failure the high authority mode isinadvertently selected in a critical phase of operation, it would resultin three times the primary control sensitivity, even for very smallinputs, resulting in degradation or possible loss of control.

To overcome the above enumerated problems the authority change mechanismof the present invention has been devised which permits the functionalrelationship between the input and output displacement to be exactly asspecified during the primary mode of operation and provides forsubstantially improved control sensitivity during the high authoritymode of operation. This is accomplished by using a relatively smallratio change mechanism 6 instead of the relatively high ratio changemechanism 5 previously used and placing the relatively low ratio changemechanism 6 in front of the cam or function generator 7 of the authoritychange mechanism 8 of the present invention as shown schematically inFIG. 4.

In FIG. 5 there is schematically illustrated one form of rotary ratiochange mechanism 6 which may be used in the authority change mechanism 8of the present invention to amplify the input signal in the secondarymode by a relatively small factor of, for instance, four to three. Theratio change mechanism 6 is of relatively simple design and includes atransfer lever 9 having a longitudinally extending slot 10 in one endfor receipt of a transverse arm 11 on one end of a ratio changemechanism actuator 12 which extends transversely into the slot 10. Aninput command is fed to the transfer lever 9 by rotation of an inputshaft 13 suitably connected to the transfer lever adjacent the other endthereof. The input to the transfer lever 9 is transferred to therotatable cam 7 by a ball joint 15 on the other end of the transferlever 9 which extends into an annular sleeve or bushing 16 carried by acrank arm 17 attached to one end of the cam.

The ratio change mechanism actuator 12 is longitudinally movable towardand away from the transfer lever 9 to change the location of the ratiochange mechanism actuator arm 11 within the slot 10 which provides amovable pivot point 18 for the transfer lever 9 whose distance to theinput transfer axis 19 varies with the change in position of the ratiochange mechanism actuator. As the distance from the pivot point 18 tothe input transfer axis 19 is increased or decreased, the ratio of theinput rotation to cam rotation is decreased or increased, respectively.

In operation of the authority change mechanism 8 of FIGS. 4 and 5, theoutput from the cam 7 is transmitted to an output shaft 20 by a camfollower 21 on the output shaft extending into a cam slot 22 in the cam.The configuration of the cam slot 22 may be such as to give the desiredoutput command to the cam follower during the primary mode of operation.A preferred input to output displacement during the primary mode ofoperation is shown in the graph in FIG. 6 and may be identical to thatfor the primary mode of conventional authority change mechanism shown inthe graph of FIG. 3. However, in the secondary mode, the output from theauthority change mechanism 8 is illustrated in the graph of FIG. 6 asbeing much less than that shown in the graph in FIG. 3 for normal inputsbecause of the use of the much smaller ratio change mechanism 6, in thisinstance, having a ratio of four to three. This has the advantage thatthe output of the authority change mechanism 8 in the secondary modedoes not exceed the maximum primary mode output authority untilapproximately percent of the maximum input is commanded, and the controlsensitivity of the secondary mode is only approximately 4/3 times thatof the normal mode up to the 75 percent input command point, which ismuch better than the control sensitivity in the secondary mode ofprevious known authority change mechanisms of the type illustrated inthe graph in FIG. 3.

Inputs beyond the 3/4 input point are not normally used during theprimary mode of operation. Accordingly, beyond the 3/4 input point tothe maximum input, the input to output ratio may be substantiallyincreased during the secondary or high authority mode by extending theinput range of the cam slot 22 at a greater angle to obtain the desiredhigh output factor at high inputs, which is the only time that theoperation in the high authority mode is critical. The portion 22 of thecam 22 from the 3/4 input point to the maximum input point is not usedin the primary mode and has the characteristic of increasing the totaloutput commanded by the desired higher factor of, for instance three,but only after the input exceeds 75 percent.

From the foregoing, it will now be apparent that the authority changemechanism of the present invention is of a relatively simple andreliable design which utilizes a relatively small ratio changer forbetter control sensitivity in the secondary mode during normal inputs upto a particular desired level, in this instance 75 percent. Beyond thatpoint the cam design has the characteristic of increasing the totaloutput commanded in the secondary mode by a much higher factor at a timewhen the high authority mode is critical.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An authority change mechanism comprising an input shaft, a cam, anoutput shaft having a cam follower engaging said cam, and a relativelylow ratio changer interposed between said input shaft and cam forslightly varying the functional relationship between input and outputdisplacement of said input shaft and cam, respectively, to provide aprimary and secondary mode of operation during inputs of less thanpercent, said cam having an extended input range extending at a greaterangle than the normal input range of said cam which provides asubstantially greater variation in the functional relationship betweeninput and output displacement in the secondary mode during higher inputsup to 100 percent.

2. The mechanism of claim 1 wherein said ratio changer includes meansfor amplifying the input signal by less than L5 to 1, and the angle ofsaid extended input range of said cam is such that in the extended rangesaid cam amplifies the input signal by a factor of at least two.

3. The mechanism of claim 2 wherein said ratio changer includes meansfor amplifying the input signal by approximately 4 to 3, and the angleof said extended input range of said cam is such that in the extendedrange said cam amplifies the input signal by a factor of approximatelythree.

4. The mechanism of claim 1 wherein said extended input range for saidcam is above 75 percent input.

5. The mechanism of claim 4 wherein the maximum input in the primarymode does not exceed 75 percent.

6. The mechanism of claim 1 wherein said ratio changer includes meansfor causing the maximum obtainable output command in the primary mode tobe achieved in the secondary mode at less than 100 percent input.

7. The mechanism of claim 6 wherein said ratio changer includes meansfor causing the maximum obtainable output command in the primary mode tobe achieved in the secondary mode at approximately percent input.

8. The mechanism of claim 1 wherein said ratio changer comprises atransfer lever having a longitudinally extending slot, a ratio changeractuator having an arm extending transversely into said slot, and meansfor moving said ratio changer actuator toward and away from saidtransfer lever to change the location of said arm within said slot whichprovides a movable pivot for said transfer lever.

9. The mechanism of claim 8 wherein said transfer lever is connected tosaid input shaft for rotation thereby, and said transfer lever is alsoconnected to said cam for transferring the input from said input shaftto said cam.

10. The mechanism of claim 9 wherein said cam has a crank arm on one endwhich supports a sleeve, and said transfer lever has a ball jointthereon extending into said sleeve for transferring the input from saidinput shaft to said cam as aforesaid.

1. An authority change mechanism comprising an input shaft, a cam, anoutput shaft having a cam follower engaging said cam, and a relativelylow ratio changer interposed between said input shaft and cam forslightly varying the functional relationship between input and outputdisplacement of said input shaft and cam, respectively, to provide aprimary and secondary mode of operation during inputs of less than 100percent, said cam having an extended input range extending at a greaterangle than the normal input range of said cam which provides asubstantially greater variation in the functional relationship betweeninput and output displacement in the secondary mode during higher inputsup to 100 percent.
 2. The mechanism of claim 1 wherein said ratiochanger includes means for amplifying the input signal by less than 1.5to 1, and the angle of said extended input range of said cam is suchthat in the extended range said cam amplifies the input signal by afactor of at least two.
 3. The mechanism of claim 2 wherein said ratiochanger includes means for amplifying the input signal by approximately4 to 3, and the angle of said extended input range of said cam is suchthat in the extended range said cam amplifies the input signal by afactor of approximately three.
 4. The mechanism of claim 1 wherein saidextended input range for said cam is above 75 percent input.
 5. Themechanism of claim 4 wherein the maximum input in the primary mode doesnot exceed 75 percent.
 6. The mechanism of claim 1 wherein said ratiochanger includes means for causing the maximum obtainable output commandin the primary mode to be achieved in the secondary mode at less than100 percent input.
 7. The mechanism of claim 6 wherein said ratiochanger includes means for causing the maximum obtainable output commandin the primary mode to be achieved in the secondary mode atapproximately 75 percent input.
 8. The mechanism of claim 1 wherein saidratio changer comprises a transfer leveR having a longitudinallyextending slot, a ratio changer actuator having an arm extendingtransversely into said slot, and means for moving said ratio changeractuator toward and away from said transfer lever to change the locationof said arm within said slot which provides a movable pivot for saidtransfer lever.
 9. The mechanism of claim 8 wherein said transfer leveris connected to said input shaft for rotation thereby, and said transferlever is also connected to said cam for transferring the input from saidinput shaft to said cam.
 10. The mechanism of claim 9 wherein said camhas a crank arm on one end which supports a sleeve, and said transferlever has a ball joint thereon extending into said sleeve fortransferring the input from said input shaft to said cam as aforesaid.